RESUMO
The risk of the use of toxic chemicals for unlawful acts has been a matter of concern for different governments and multilateral agencies. The Organisation for the Prohibition of Chemical Weapons (OPCW), which oversees the implementation of the Chemical Weapons Convention (CWC), considering recent events employing chemical warfare agents as means of assassination, has recently included in the CWC "Annex on Chemicals" some organophosphorus compounds that are regarded as acting in a similar fashion to the classical G- and V-series of nerve agents, inhibiting the pivotal enzyme acetylcholinesterase. Therefore, knowledge of the activity of the pyridinium oximes, the sole class of clinically available acetylcholinesterase reactivators to date, is plainly justified. In this paper, continuing our research efforts in medicinal chemistry on this class of toxic chemicals, we synthesized an A-230 nerve agent surrogate and applied a modified Ellman's assay to evaluate its ability to inhibit our enzymatic model, acetylcholinesterase from Electrophorus eel, and if the clinically available antidotes are able to rescue the enzyme activity for the purpose of relating the findings to the previously disclosed in silico data for the authentic nerve agent and other studies with similar A-series surrogates. Our experimental data indicates that pralidoxime is the most efficient compound for reactivating acetylcholinesterase inhibited by A-230 surrogate, which is the opposite of the in silico data previously disclosed.
Assuntos
Acetilcolinesterase , Substâncias para a Guerra Química , Inibidores da Colinesterase , Reativadores da Colinesterase , Agentes Neurotóxicos , Oximas , Compostos de Piridínio , Oximas/farmacologia , Acetilcolinesterase/metabolismo , Reativadores da Colinesterase/farmacologia , Inibidores da Colinesterase/toxicidade , Compostos de Piridínio/farmacologia , Substâncias para a Guerra Química/toxicidade , Agentes Neurotóxicos/toxicidade , Compostos de Pralidoxima/farmacologia , Compostos Organotiofosforados/toxicidade , Animais , Antídotos/farmacologiaRESUMO
The A-series is the most recent generation of chemical warfare nerve agents (CWA) which act directly on the inhibition of the human acetylcholinesterase (HssAChE) enzyme. These compounds lack accurate experimental data on their physicochemical properties, and there is no evidence that traditional antidotes effectively reactivate HssAChE inhibited by them. In the search for potential antidotes, we employed virtual screening, molecular docking, and molecular dynamics (MD) simulations for the theoretical assessment of the performance of a library of Mannich phenols as potential reactivators of HssAChE inhibited by the Novichok agents A-230, A-232, and A-234, in comparison with the commercial oximes pralidoxime (2-PAM), asoxime (HI-6), trimedoxime (TMB-4), and obidoxime. Following the near-attack conformation (NAC) approach, our results suggest that the compounds assessed would face difficulties in triggering the proposed nucleophilic in-line displacement mechanism. Despite this, it was observed that certain Mannich phenols presented similar or superior results to those obtained by reference oximes against A-232 and A-234 model, suggesting that these compounds can adopt more favourable conformations. Additional binding energy calculations confirmed the stability of the model/ligands complexes and the reactivating potential observed in the molecular docking and MD studies. Our findings indicate that the Mannich phenols could be alternative antidotes and that their efficacy should be evaluated experimentally against the A-series CWA.
Assuntos
Substâncias para a Guerra Química , Reativadores da Colinesterase , Agentes Neurotóxicos , Humanos , Antídotos/farmacologia , Reativadores da Colinesterase/farmacologia , Acetilcolinesterase/metabolismo , Simulação de Acoplamento Molecular , Inibidores da Colinesterase/farmacologia , Inibidores da Colinesterase/química , Oximas/farmacologia , Oximas/química , Trimedoxima/química , Trimedoxima/farmacologia , Substâncias para a Guerra Química/farmacologia , Compostos de Piridínio/farmacologiaRESUMO
Organophosphorus compounds (OP) make up an important class of inhibitors, mostly employed as pesticides, even as chemical weapons. These toxic substances act through the inhibition of the acetylcholinesterase (AChE) enzyme, which results in elevated synaptic acetylcholine (ACh) levels, leading to serious adverse effects under the cholinergic syndrome. Many reactivators have been developed to combat the toxic effects of these AChE inhibitors. In this line, the oximes highlight because of their good reactivating power of cholinesterase enzymes. To date, no universal antidotes can reactivate AChE inhibited by any OP agent. This review summarizes the intoxication process by neurotoxic OP agents, along with the development of reactivators capable of reversing their effects, approaching aspects like the therapeutic and toxicological profile of these antidotes. Computational methods and conscious in vitro studies, capable of significantly predicting the toxicological profile of these drug candidates, might support the process of development of these reactivators before entering in vivo studies in animals, and then clinical trials. These approaches can assist in the design of safer and more effective molecules, reducing related cost and time for the process.
Assuntos
Antídotos , Reativadores da Colinesterase , Animais , Antídotos/farmacologia , Antídotos/uso terapêutico , Antídotos/química , Acetilcolinesterase/química , Reativadores da Colinesterase/uso terapêutico , Reativadores da Colinesterase/toxicidade , Compostos Organofosforados , Oximas/uso terapêutico , Oximas/toxicidade , Inibidores da Colinesterase/toxicidadeRESUMO
The misuse of novichok agents in assassination attempts has been reported in the international media since 2018. These relatively new class of neurotoxic agents is claimed to be more toxic than the agents of the G and V series and so far, there is no report yet in literature about potential antidotes against them. To shed some light into this issue, we report here the design and synthesis of NTMGMP, a surrogate of A-242 and also the first surrogate of a novichok agent useful for experimental evaluation of antidotes. Furthermore, the efficiency of the current commercial oximes to reactivate NTMGMP-inhibited acetylcholinesterase (AChE) was evaluated. The Ellman test was used to confirm the complete inhibition of AChE, and to compare the subsequent rates of reactivation in vitro as well as to evaluate aging. In parallel, molecular docking, molecular dynamics and MM-PBSA studies were performed on a computational model of the human AChE (HssAChE)/NTMGMP complex to assess the reactivation performances of the commercial oximes in silico. Experimental and theoretical studies matched the exact hierarchy of efficiency and pointed to trimedoxime as the most promising commercial oxime for reactivation of AChE inhibited by A-242.
Assuntos
Reativadores da Colinesterase , Agentes Neurotóxicos , Acetilcolinesterase , Antídotos/farmacologia , Inibidores da Colinesterase/toxicidade , Reativadores da Colinesterase/farmacologia , Humanos , Simulação de Acoplamento Molecular , Agentes Neurotóxicos/toxicidade , Oximas/farmacologiaRESUMO
Organophosphorus poisoning caused by some pesticides and nerve agents is a life-threating condition that must be swiftly addressed to avoid casualties. Despite the availability of medical countermeasures, the clinically available compounds lack a broad spectrum, are not effective towards all organophosphorus toxins, and have poor pharmacokinetics properties to allow them crossing the blood-brain barrier, hampering cholinesterase reactivation at the central nervous system. In this work, we designed and synthesised novel isatin derivatives, linked to a pyridinium 4-oxime moiety by an alkyl chain with improved calculated properties, and tested their reactivation potency against paraoxon- and NEMP-inhibited acetylcholinesterase in comparison to the standard antidote pralidoxime. Our results showed that these compounds displayed comparable in vitro reactivation also pointed by the in silico studies, suggesting that they are promising compounds to tackle organophosphorus poisoning.
Assuntos
Acetilcolinesterase/efeitos dos fármacos , Reativadores da Colinesterase/farmacologia , Isatina/farmacologia , Piridinas/farmacologia , Simulação por Computador , Técnicas In VitroRESUMO
BACKGROUND: Neurotoxic chemical warfare agents can be classified as some of the most dangerous chemicals for humanity. The most effective of those agents are the Organophosphates (OPs) capable of restricting the enzyme Acetylcholinesterase (AChE), which in turn, controls the nerve impulse transmission. When AChE is inhibited by OPs, its reactivation can be usually performed through cationic oximes. However, until today, it has not been developed one universal defense agent, with complete effective reactivation activity for AChE inhibited by any of the many types of existing neurotoxic OPs. For this reason, before treating people intoxicated by an OP, it is necessary to determine the neurotoxic compound that was used for contamination, in order to select the most effective oxime. Unfortunately, this task usually requires a relatively long time, raising the possibility of death. Cationic oximes also display a limited capacity of permeating the Blood-Brain Barrier (BBB). This fact compromises their capacity to reactivating AChE inside the nervous system. METHODS: We performed a comprehensive search on the data about OPs available on the scientific literature today in order to cover all the main drawbacks still faced in the research for the development of effective antidotes against those compounds. RESULTS: Therefore, this review about neurotoxic OPs and the reactivation of AChE, provides insights for the new agents' development. The most expected defense agent is a molecule without toxicity and effective to reactivate AChE inhibited by all neurotoxic OPs. CONCLUSION: To develop these new agents, the application of diverse scientific areas of research, especially theoretical procedures as computational science (computer simulation, docking and dynamics), organic synthesis, spectroscopic methodologies, biology, biochemical and biophysical information, medicinal chemistry, pharmacology and toxicology, is necessary.
Assuntos
Acetilcolinesterase , Reativadores da Colinesterase , Inibidores da Colinesterase/toxicidade , Reativadores da Colinesterase/farmacologia , Simulação por Computador , Humanos , Compostos Organofosforados/toxicidade , Oximas/farmacologiaRESUMO
Organophosphorus (OP) compounds are used as both chemical weapons and pesticides. However, these agents are very dangerous and toxic to humans, animals, and the environment. Thus, investigations with reactivators have been deeply developed in order to design new antidotes with better efficiency, as well as a greater spectrum of action in the acetylcholinesterase (AChE) reactivation process. With that in mind, in this work, we investigated the behavior of trimedoxime toward the Mus musculus acetylcholinesterase (MmAChE) inhibited by a range of nerve agents, such as chemical weapons. From experimental assays, reactivation percentages were obtained for the reactivation of different AChE-OP complexes. On the other hand, theoretical calculations were performed to assess the differences in interaction modes and the reactivity of trimedoxime within the AChE active site. Comparing theoretical and experimental data, it is possible to notice that the oxime, in most cases, showed better reactivation percentages at higher concentrations, with the best result for the reactivation of the AChE-VX adduct. From this work, it was revealed that the mechanistic process contributes most to the oxime efficiency than the interaction in the site. In this way, this study is important to better understand the reactivation process through trimedoxime, contributing to the proposal of novel antidotes.
Assuntos
Reativadores da Colinesterase/química , Trimedoxima/farmacologia , Trimedoxima/uso terapêutico , Acetilcolinesterase/metabolismo , Animais , Antídotos/farmacologia , Inibidores da Colinesterase/metabolismo , Inibidores da Colinesterase/farmacologia , Reativadores da Colinesterase/farmacologia , Biologia Computacional/métodos , Humanos , Camundongos , Agentes Neurotóxicos/química , Compostos Organofosforados/química , Oximas/química , RatosRESUMO
Acetylcholinesterase (AChE) is the key enzyme responsible for deactivating the ACh neurotransmitter. Irreversible or prolonged inhibition of AChE, therefore, elevates synaptic ACh leading to serious central and peripheral adverse effects which fall under the cholinergic syndrome spectra. To combat the toxic effects of some AChEI, such as organophosphorus (OP) nerve agents, many compounds with reactivator effects have been developed. Within the most outstanding reactivators, the substances denominated oximes stand out, showing good performance for reactivating AChE and restoring the normal synaptic acetylcholine (ACh) levels. This review was developed with the purpose of covering the new advances in AChE reactivation. Over the past years, researchers worldwide have made efforts to identify and develop novel active molecules. These researches have been moving farther into the search for novel agents that possess better effectiveness of reactivation and broad-spectrum reactivation against diverse OP agents. In addition, the discovery of ways to restore AChE in the aged form is also of great importance. This review will allow us to evaluate the major advances made in the discovery of new acetylcholinesterase reactivators by reviewing all patents published between 2016 and 2019. This is an important step in continuing this remarkable research so that new studies can begin.
Assuntos
Acetilcolinesterase/metabolismo , Reativadores da Colinesterase , Reativadores da Colinesterase/química , Reativadores da Colinesterase/uso terapêutico , Proteínas Ligadas por GPI/metabolismo , Humanos , Oximas/química , Oximas/uso terapêutico , Patentes como AssuntoRESUMO
The inhibition of acetylcholinesterase (AChE) is a common outcome caused by organophosphorus (OPs) intoxication. Although inconsistent, the standard treatment consists of a muscarinic receptor antagonist (atropine) and AChE-reactivating molecules such as oximes. This study proposes to test unpublished compounds which contain the moieties of isatin and/or oxime have protective effects against the toxicity induced by malathion in two animal models: Artemia salina and Rattus norvegicus (Wistar rats). The lethality was assessed in A salina, and the calculated LD50 to (3Z)-5-chloro-3-(hydroxyimino) indolin-2-one oxime (Câ-HIN) and 2-(5-chloro-2-oxoindolin-3-ylidene)-hydrazinecarbothioamide (Câ-OXHS) was higher than 1000 µM while to 3-(phenylhydrazono) butan-2-one oxime (PHBO) was 38 µM. Our screening showed that Câ-HIN seems to be the most promising molecule, with low toxicity to A salina, protection against mortality (with or without atropine) and AChE inhibition induced by malathion. Similarly, the oral administration of 300 mg/kg of Câ-HIN induced low or no toxicity in rats. The plasma butyrylcholinesterase (BChE) and cortical AChE activities were reactivated by Câ-HIN (50 mg/kg, p.o.) in rats exposed to malathion (250 mg/kg, i.p). No difference was observed in paraoxonase-1 (PON-1) activity among groups treated. In conclusion, Câ-HIN restored the cholinesterase activities inhibited by malathion in A salina and rats with low toxicity in both. Thus, the data provide evidence that Câ-HIN, a compound that combines isatin and oxime functional groups, is safe and has important properties to reactivate the cholinesterases inhibited by malathion. In addition, we demonstrate the importance of a preliminary assessment in an alternative model in order to reduce the use of mammalians in drug discovery.
Assuntos
Inibidores da Colinesterase/toxicidade , Isatina/farmacologia , Malation/toxicidade , Oximas/farmacologia , Animais , Artemia , Reativadores da Colinesterase/administração & dosagem , Reativadores da Colinesterase/química , Reativadores da Colinesterase/farmacologia , Modelos Animais de Doenças , Descoberta de Drogas/métodos , Feminino , Inseticidas/toxicidade , Isatina/administração & dosagem , Isatina/química , Dose Letal Mediana , Masculino , Oximas/administração & dosagem , Oximas/química , Ratos , Ratos WistarRESUMO
Studies with oximes have been extensively developed to design new reactivators with better efficiency, and greater spectrum of action. In this study, we aimed to analyze the influence of the Carbamoyl group position change in two isomeric oximes, K203 and K206, on the reactivation percentage of Mus musculus Acetylcholinesterase (MmAChE), inhibited by different nerve agents. Theoretical calculations were performed to assess the difference for the oxime activity with inhibited AChE-complexes and the factors that govern this difference. Comparing theoretical and experimental data, it is possible to observe that this change between the oximes results in different reactivation percentage for the same nerve agent, due to the different interaction modes and activation energy for the studied systems.